NON-CONFIDENTIAL INVENTION DISCLOSURES
Individuals interested in more information should contact
Ms. Laurel Halfpap Phone: 541-737-4437 Senior Licensing Associate Fax: 541-737-3093 Office of Technology Transfer Oregon State University 312 Kerr Administration Bldg. Corvallis, Oregon 97331-2140 e-mail Laurel.Halfpap@orst.edu Home Page http://osu.orst.edu/research/techTransfer.html
1. Non-Confidential Invention Disclosure For Redox Indicators
Professor James Ingle and Brian Jones, Inventors
Inventors at Oregon State University have developed immobilized redox indicators in a physical form suitable for practical use in the field and the laboratory. These indicators can be used for monitoring parameters such as redox status in field samples (e.g., ground water, wells, lakes, oceans, rivers, and streams) and laboratory samples (bioreactors, microcosms) and the dominant microbial redox process in those samples. Such devices could be used for initial assessment of field sites or laboratory samples and for continuous monitoring of the progress of remediation of a contaminant in the field. Such devices would be useful to environmental engineers, soil scientists, microbiologists, limnologists, public health workers, oceanographers, and operators of drinking water, wastewater, and paper and pulp facilities.
The redox indicators immobilized in a physical format could be the basis of field instruments and probes for measuring redox status or “redox potential” and replace the Pt electrode. These devices would be relatively simple and inexpensive and not require any sample manipulation such as addition of reagents. These new instruments would provide a more accurate method for evaluating redox status in the field than the Pt electrode; a major advantage over the Current Technology described below.
Redox indicators are compounds that are normally colored in their oxidized form and colorless when reduced. Their absorbance can be monitored spectrophotometrically (or observed visually) as they react reversibly with reductants or oxidants in a sample. The absorbance of a given indicator decreases when conditions become sufficiently reducing and can be used to define a “redox potential.” This “redox potential” can provide information about the status of a sample including the absence or presence of certain reductants (e.g., Fe (II)) or oxidants (e.g., O2) or the type of microbial process (e.g., Fe (III)-reducing conditions) that is dominant in the sample.
Redox indicators have a tendency to strongly adsorb on natural samples (e.g., soil). Hence for many applications, a redox indicator must be immobilized such that it does not leach out into the sample and can be used repeatedly for monitoring a parameter over a period of time. It is possible to evaluate the redox status of a sample by pumping a filtered sample from a slurry through a flow cell packed with small porous beads on which a redox indicator has been immobilized. Unfortunately, flow rates are low and clogging is a problem.
The inventors have immobilized redox indicators in a non-bead physical form which allows the use of high sample flow rates, little or no filtering, exposure of the redox indicator to both dissolved and adsorbed redox-active species and microbes in the sample, and minimal clogging by particulate matter in the sample. This physical format allows the redox indicator to be used in a flow cell over a long period of time in a reversible manner and in other unique sensor configurations.
It has been demonstrated that immobilized redox indicators can cover a wide range of redox potentials (+100 mV to -300 mV). Redox indicators can be used to identify microbial redox conditions (e.g., Fe (III)-reducing, sulfate-reducing, methanogenesis). The reduction of an indicator is a positive and unambiguous indication that certain reductants are present in a sample. Additionally, it has been demonstrated that immobilized indicators can be used for semi-quantitative determination of major reductants including Fe(II), S(-II), and H2 and oxidants including O2, H2O2, and Cr(VI). Specific redox indicators respond reversibly to the Fe(II)/Fe(III)(OH)3 couple), can provide detection of trace levels of sulfide (< 1 mM), and can be used to predict when contaminants are reduced (e.g., As(V) is reduced to As(III), TCE is reduced to cis-DCE).
CURRENT TECHNOLOGY
Today there are two “accepted” methods and one proposed method for measuring redox status, all with substantial limitations. The most common method for determining ‘redox potential’ (oxidation-reduction potential (ORP)) involves measuring the potential of a Pt electrode (redox electrode) when inserted into a sample (corrected for reference electrode potential). It has been established that the electrode does not perform adequately for environmental measurements and that the absolute potential of the electrode does not necessarily reflect the redox state of many species in the sample or indicate the dominant microbial process. The second “method” involves measurement of the concentrations of 5 to 15 species in the sample that are involved in redox transformations, an expensive and time-consuming process which requires that the sample be returned to the laboratory. A third and more recently proposed method is that of measuring H2 in the sample which requires a time-consuming gas headspace sampling step and a GC with a special reduction gas detector (costing as much as $18,000).
The Oregon State University redox indicators are simple and inexpensive, provide a more accurate method for evaluating redox status in the field than the Pt electrode, and do not require any sample manipulation such as addition of reagents.
2. Non-Confidential Invention Disclosure Redox Potential Sensors
James Ingle and Kevin Cantrell, Inventors
Summary:
Inventors at Oregon State University have developed sensors based on immobilized redox indicators suitable for use in the field and laboratory. These sensors can be used for the monitoring of parameters in various exposure environments including laboratory vessels, flow streams, and field sites. These probes measure redox status or “redox potential” and would be useful to environmental engineers, soil scientists, microbiologists, limnologists, public health workers, oceanographers, and operators of drinking water, wastewater, and paper and pulp facilities. These devices are relatively simple, inexpensive, do not require sample manipulation, and offer advantages compared to traditional redox measurements based on Pt electrodes (ORP). In addition, these devices could serve as monitors in anaerobic systems to indicate the intrusion of oxygen.
Features:
All devices are miniaturized for in-situ monitoring of the color changes of an immobilized redox reagent. Embedded micro controllers are used for control of the optical sources and detectors and data acquisition, processing, and storage. In particular, these devices are suitable for monitoring anaerobic samples in closed systems to minimize exposure of the sample to oxygen. Such environments include:
1) laboratory vessels (e.g., microcosm bottles, bioreactors),
2) flow streams (e.g., water pumped from and into wells, outlet flow from columns and laboratory models for aquifer systems, water pumped to and from laboratory bioreactors), and
3) sub-surface systems in which the sensor is deployed in direct contact with the sample (in-situ) without pumping (e.g., driven into the ground or sediment, submerged in a water sample or a sampling well without pump).
The sensors are designed as stand alone, portable, and adaptable field sensors and include features such as data logging, automated sampling, a computer interface, and user-selectable parameters. These devices respond reversibly to changes in redox conditions and appear to provide a more accurate method for evaluating redox status than the Pt electrode.
Redox Measurements:
Among the most important factors controlling the persistence, mobility, and biological effects of many organic and inorganic contaminants are oxidation-reduction (redox) transformations. Redox potential can provide information about the status of a sample including the dominant microbial process or the absence or presence of certain reductants or oxidants. The degradation rates and pathways of organic compounds are known to depend strongly on ambient redox conditions. In the design of in-situ remediation strategies, control of the predominant redox processes and microbial metabolism through the proper balance of carbon substrate and the terminal electron acceptor is critical in obtaining the desired transformation of an organic contaminant. Microbial redox conditions easily measured with these sensors include Fe (III)-reducing, sulfate-reducing, and methanogenesis. For inorganic chemicals, speciation, and hence transport and biological effects, depends strongly on redox reactions. Anyone who studies biological or environmental processes could benefit from these redox sensors and gain a clearer understanding of the conditions under which redox transformations occur.